UPSC Prelims 2021 Question:

In case of which of the following biogeochemical cycles, the weathering of rocks is the main source of release of nutrients to enter the cycle?

Explanation:

• Phosphorus Cycle is a biogeochemical cycle in which Phosphorus travels through the Lithosphere, Biosphere, and Hydrosphere.
  
  
• Phosphorus is found in nature in the form of rock. The rock contains phosphorus in the form of phosphates. Due to weathering of rocks, phosphates mix with the soil, which gets absorbed by the plants in the form of a solution. Herbivores and other carnivores obtain this phosphorus through the food chain. After the death of these animals, phosphorus again enters the soil through the decomposition process.
  
  
• Carbon cycle involves a continuous exchange of carbon between the atmosphere and organisms. The nitrogen cycle is a repeating cycle of processes during which nitrogen moves through both living and non-living things. Both carbon and nitrogen cycles are the gaseous cycles. Here, the main reservoir of nutrients is the atmosphere or the hydrosphere. 
  
  
• The sulfur cycle is a biogeochemical cycle in which the sulfur moves between rocks, waterways and living systems. The nutrients are released by weathering of rocks, erosional runoff and decomposition of organic matter. The sulphur cycle is mostly sedimentary but two of its compounds hydrogen sulphide (H2S) and sulphur dioxide (SO2) add a gaseous component to its normal sedimentary cycle. 
  
  

Therefore, option (3) is the correct answer.

Subject: Environment | Ecology